Types of Attackers

Speaking in a very generalizing way, below are some common types of attackers:

1. Individuals. The very first computer attackers were individuals, who committed these actions for fun, to show off, for challenge, to test their own abilities, and sometimes out of revenge. Two famous individual attackers are Robert Morris and Kevin Mitnick.
2. Organized, Worldwide Groups. Groups of loosely-connected international groups of hackers conducted more recent attacks. "Loosely-connected" means that the attackers don't know other attackers in that group very well and that they aren't restricted from leaving the group whenever they want and joining other such groups. The motives of such groups in unleashing attacks are mostly financial: they 'join forces' to attack systems or companies to steal money, e.g., by stealing customer credit card information.
3. Organized Crime Groups. The goal of such criminals isn't damaging a computer or system but turning that computer into a money-making target. For instance: by secretly stealing credit card information over a period of time without being detected or demanding ransom for data they stole and encrypted, and also selling the data.